A potent mitogenic polypeptide present in mammalian Sertoli cells is to be purified to homogeneity on a preparative scale from calf testes. This objective is to be accomplished using a purification sequence involving chromatography on Bio-Gel P-150, dodecyl-agarose, diethylaminoethyl sephadex and hydroxyapatite, and by preparative isoelectric focusing. If necessary, SDGF will be purified further by affinity chromatography using an antibody specific for the polypeptide. Purity of the SDGF is to be assessed using SDS-polyacrylamide gel electrophoresis, amino acid analysis and amino- and carboxy-terminal analyses. Monoclonal antibodies directed against SDGF shall be produced using the hybridoma technique and antibody-producing cultures selected by utilizing a sensitive solid phase immunoassay. Once characterized, the monospecific antibodies will be applied a) to study the differential effect of SDGF and PDGF on Sertoli cells at the molecular level, b) to determine whether Sertoli cells synthesize SDGF and c) to identify other target cells within the testis.